Five charts on the changing Midwestern climate ⋆

The just-released Fifth National Climate Assessment contains some grim predictions about the future climate trajectory of the Midwest and the country as a whole. Temperatures are warming, environments are degrading, and the world we once knew is evolving into something very different.

The report also contains a lot of charts, and in many cases those charts paint the picture of climate change more vividly than the report’s lengthy text. Here are a few of our favorites.

Spring thaws are happening earlier

Fifth National Climate Assessment chart

The chart on the left shows the trend in the last spring freeze and frost dates for Leelanau county in Michigan. In the 1950s, for instance, you could expect the last day of 32 degree temperatures to happen in the latter half of May. Now, however, it tends to happen in the beginning of the month.

The map on the right shows the trend for all counties in the Midwest since 1950. While there are exceptions, most counties are seeing the growing season begin several days earlier than before.

The Midwestern Regional Climate Center has an online tool you can use to see how growing seasons have shifted in your county.

Lyme disease on the march

Fifth National Climate Assessment chart

This chart plots the staggering increase in Lyme disease cases in the Midwest since 2000. Back then there were typically between 1,000 and 1,500 Lyme cases in the region in any given year. Now there are usually more than 5,000.

Rising temperatures and precipitation, along with milder winters and land-use changes, have conspired to make the region a more hospitable habitat for the ticks that harbor the disease. Projections suggest this trend will continue.

Warming waters

Fifth National Climate Assessment chart

Since 1980, summer surface water temperatures have risen by close to 5 degrees Fahrenheit in Lake Superior and Lake Huron, and by a slightly smaller amount in Lake Michigan and Lake Erie. These increased temperatures contribute to lower water levels by increasing evaporation rates, and they cause lake ice to form later in the winter.

Overall, “the Great Lakes are frozen for eight to 46 fewer days now than they were in the early 1970s,” the Environmental Protection Agency reports. This creates a more inviting environment for invasive species like zebra mussels, and it encourages the growth of certain types of bacteria and algae that can be harmful to humans and wildlife.

Flood. Drought. Repeat.

Fifth National Climate Assessment chart

These maps plot the annual frequency of transitions between extreme wet and dry periods in the present (left-most map), and under varying climate scenarios. The short version of this story is that the hotter it gets, the more rapidly those transitions will occur.

This will wreak havoc not just on the natural environment, but also the human landscape. Fields and cities will flood more often, and be subject to more droughts, too. Crop yields will become more variable year-over-year, and municipalities will incur staggering bills to cover flood mitigation and cleanup. Wells will run dry, and water shortages will become more common.

More runoff

Fifth National Climate Assessment chart

Runoff — a measure of the movement of water above and below the surface throughout the year — is expected to increase considerably in the coming decades, especially during the winter. This will cause some of the flooding alluded to above. It’ll also carry more pollutants from agricultural operations deep into the groundwater, where it’ll be able to poison more drinking water wells.

The net effect, according to the report: “increased stresses to ecosystems, the built environment, natural and water resources, and agriculture.”

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authored by Christopher Ingraham
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